Ease my mind: oil light edition

Alright guys, I need someone to tell me that I am not crazy. I've noticed that on really cold days, the oil pressure light on my `99 Grand Marquis likes to act up. It will usually stay on after start-up and it stays on regardless of engine temp or speed. The oil was changed at a Ford dealership upon my purchase and the correct weight/viscosity was used. I've put over 1k on the car since, and the oil is at the correct level and still looks 'good'.

It did it again today, and stayed on for a good chunk of my 80 mile trip. It would flicker when driving over bumps, and go out completely for little lengths of time. I highly doubt there's anything actually wrong with my pressure, given the erratic behavior of the light, but I am curious what you guys think. I will try and get it into a shop this week, but I still want to possibly sleep well tonight.

An oil light is usually a bad switch, sometimes a pinched wire. Bump-based activation hints at pinched/chafed wire.

Science experiment: Next time the light's on, give the dashboard over the instrument panel a few good solid whacks with your hand.

Senders are usually under $20, might as well.

wouldn't be the first time a sender went bad

depending on location of sender, connector housing may be brittle from heat and allowing the terminal to break contact occasionally. had that prob on '68 mustang 302 recently.

Thanks guys, I feel much better knowing that it's most likely the sender.

Do you hear a terrible rattling? A deep, hammering roar? Are you inexplicably down on power?

I'd drain the oil and look for bearings.

chaparral wrote: Do you hear a terrible rattling? A deep, hammering roar? Are you inexplicably down on power? I'd drain the oil and look for bearings.

I imagine he would've mentioned noises like those.

Alan Cesar wrote:

chaparral wrote: Do you hear a terrible rattling? A deep, hammering roar? Are you inexplicably down on power? I'd drain the oil and look for bearings.

I imagine he would've mentioned noises like those.

One hopes!

However a pressure check would put my mind at ease, and most likely not real expensive.

Haha, no death noises or loss of power here. I would have been more worried if the oil light came on at hot idle in gear.

I forgot to note that after I washed it yesterday, the light stayed off. And no, the bulb did not burn out.

Sounds like a sender. Speaking of oil senders the cadillacs of the early 80's took the oil pressure sender thing one step further. They had one that if it got below a certain PSI it killed the ignition. I picked up 4 cars that way. One I jacked up the car in the sellers yard and drive it away after giving him a $100 (the car was mint). The sender was made of bakelite and it would disintegrate due to the heat of the exhaust manifold being next to it (a heat shield solved the problem)

On the other side of this I went to look at one and it was being sold by an elderly couple. They told me that the local shop wanted $1500 for a new fuel system and that is why they were letting there "baby" go. I did not have the heart to take it. I fixed it in there garage (by that time I would keep a spare sender in one back pocket and the wrenches to remove and replace it in the other). They offered me $500 for 15 min work. I declined it was great to see how happy they were. They loved that car. The elderly man insisted that he get my name address and phone and later that week a bottle of single malt scotch showed up with a thank you note attached. I completely forgot about it and had since moved on to RX'7s but about 4-5 years later I got a call from there daughter saying that her father had passed and there mother could not drive and they were getting rid of the car. They had found a note attached to the title telling them to call me if the car was to be sold. I told them the story and they insisted that I keep the car. I drove that car for another 2-3 years until it finally rusted out from under me. I was sad to see it go. I still have an alternator bracket from that car.. Funny how little things become important.

Sorry for getting side tracked here but your oil sender problems reminded me of this little story.

I'm not going to lie, that's a pretty awesome story.

Great story. Shows the high caliber of the folks here on GRM.

Alan Cesar wrote:

chaparral wrote: Do you hear a terrible rattling? A deep, hammering roar? Are you inexplicably down on power? I'd drain the oil and look for bearings.

I imagine he would've mentioned noises like those.

Experience is that even when the cam "bearings" are super trashed and/or there is a rod knock so loud even my deaf aunt can hear it, these engines will still have plenty of hot idle oil pressure...

In reply to dean1484:

Great post. Would read again.

yes it was ... one question ... how pissed were the owners of the one you paid $100 for ?

wbjones wrote: yes it was ... one question ... how pissed were the owners of the one you paid $100 for ?

Yea, unless they were a dick, I probably would have spent $50 on a tow to get it out of sight.

Almost forgot to update, but it turned out to be the sender. Oil pressure is just fine.

spitfirebill wrote:

wbjones wrote: yes it was ... one question ... how pissed were the owners of the one you paid $100 for ?

Yea, unless they were a dick, I probably would have spent $50 on a tow to get it out of sight.

why? maybe they will learn a lesson and get things checked out better next time..

yeah, i'm a cold hearted SOB when it comes to these things.. i once got a car (i forget which one- after 22 years and no less than a couple hundred cars, they kind of blend in together) that developed a miss after a new set of spark plug wires were installed... the owner figured the shop screwed something up, so he sold it to me cheap... it was a rusted out Chevy something or other with a 350 in it. might have been the 74 El Camino, now that i think about it.. anyways, i listened to the engine, revved it up and what not... paid the guy something like $200 (again, it was a couple of decades ago and i've had a LOT of cars come and go) and once i had the signed title in hand i switched the 5 and 7 plug wires and drove it away without a single miss, pop, or backfire...